The invention relates to the automation of scarfing surface defects of a metal piece such as steel slab, for example.
In the prior art practice the scarfing or cutting of a metal piece such as steel slab to remove surface defects has been accomplished by sensing the position, extent, type and depth of surface defects through manual intervention and manually operating a scarfing nozzle or cutting machine. For removal of surface defects of the metal piece, it is impossible to determine the scarfing procedure within a sufficiently short time interval which would allow the defects dispersed along the slab surface to be scarfed within the minimum period of time. As a result, the machine capability is constrained by the human ability. Where the scarfing machine includes a plurality of nozzles, a manual operation of issuing simultaneous scarfing instructions to the plurality of nozzles becomes even more difficult, the more the number of nozzles, thereby precluding an efficient scarfing treatment.
Another factor which stands in the way of the automation of the control of the scarfing machine has been the lack of an effective recognition system which deals with information representing the surface defects of the metal piece.
Hand scarfing is unfavorable from the standpoint of the health administration of operators, and is also limited in the processing capability.
In view of the difficulties mentioned above in connection with the conventional method of treating surface defects of a metal piece, it is an object of the invention to provide a process of treating surface defects of a metal piece which can be automated to a high level.
The Japanese patent specification No. 277,271 describes a method and apparatus for automated scarfing of surface defects of a metal piece. In the method, single color marks are spread on defects of a metal surface by workers, or luminous substance is impregnated in the defects of a metal surface automatically. Photo-sensitive means detects the marks or luminous substance. Detected signals of the photo-sensitive means are recorded on electro-magnetic tape or tapes. The tapes travels in synchronism with the movement of the metal piece. The recorded signals on the tapes are then read out at the scarfing position to scarf the defects on which the marks or luminous substance are spread or impregnated. A time adjustment means to determine the scarfing position includes the tapes and driving mechanism for the tapes. The time adjusting means determines the time interval between the detection of the defects by the photo-sensitive means and triggering of scarfing. Thus, the defects detected by the photo-sensitive means are deleted out by scarfers at the lower reaches of the metal transmitting path. However, the metal piece travels continuously, so that defects at the head end position of the metal piece can not be deleted out thoroughly, because heating of the metal surface by scarfers is not sufficient at the top (head) edge of the metal piece when the metal piece is moving.
Therefore it is preferable to scarf out thoroughly the defects near the top edge of the metal piece.
In another point of view, scarfers have delay times to scarfing out the defects sufficiently, so that when defects exist hear and there, defects which reach the scarfing position within a delay time from a preceeding defect can not be scarfed out thoroughly. In addition, marks spread on the metal surface or luminous substance impregnated in the defects are not uniform, and have breaks, so that scarfings may stop in intermediate positions of the defects. Therefore, stable and uniform scarfing upon a continuous defect is frequently not achieved.
Further, the metal piece may sway in transverse direction, so that modification of the scarfer's position in the transverse direction may be required.